Construction of tunnels



(No Model.) I

G G. GILMAN.

CONSTRUCTION OF TUNNELS.

Patented July 6, v 1886.

mmm nv r. Wu

UNITED STATES PATENT OFFICE.

CHARLES CARROLL GILMAN, OF ELDORA, IOWA.

CONSTRUCTION OF TUNNELS.

SPECIFICATION forming part of Letters Patent No. 345,046, dated July 6,1886.

Application filed April 2, 1886. Serial No. 197,541. (No model.)

the wires devoted to electrical service that may be placed therein, andto accomplish these results by a construction which is light,indestructible, and relatively inexpensive.

To this end my invention consists in providing a brick or stone tunnel,subway, or arch with a lining of terra-cotta lumber or a porous earthenware prod uct saturated or deeply coated with asphalt.

In the accompanying drawing, forming part of the specification, isrepresented a crosssection of an arch, subway, or tunnel constructed inaccordance with my invention.

In said drawing, A represents the stone or brick work of the tunnel, andB the blocks of terra-cotta lumber, saturated or deeply coated withasphalt. The tcrra-cotta lumber which I use must be distinguished fromordinary terra-cotta. The latter is porous, but only to a slight extentas compared with the former. The terra-cotta lumberis produced by mixingvegetable with earthen matter and burning out the vegetable matter inthe kiln, leaving the material extremely porous, the degree of porositydepending upon the proportion of vegetable to earthen matter. Thismaterial is not materially affected by heat or cold, is a non-conductorof electricity, and can be saturated or deeply coated with asphalt. Thesaturation or impregnation of the material with asphalt is mostthoroughly accomplished by heating it in an exhausted receiver andadmitting the asphalt thereto while the air is exhausted and thematerial in a heated condition. I line or form the inner surface of asubway, arch, or tunnel of this porous material saturated or deeplycoated with asphalt. I bond the blocks with asphalt, instead of withcement or mortar, and thus secure a tight and waterproof joint. As theblocks of terracotta lumber are saturated or deeply coated with asphalt,and as they are united by a bond of the same material, there is nopossibility of any leakage of water from the surrounding earth into thetunnel. The blocks may be laid upon each other and held in place by thekey-stone, as illustrated 1n the drawing, or they may be nailed orotherwise secured to the mortarjoints of the brick or stone work, as theterra-cotta lumber will readily receive nails. In carrying wires for theelectrical service through such a tunnel it is unnecessary to take theusual p recautions to secure insulation, as both the terracotta lumberand the asphalt are bad conductors of electricity, and it will only benecessary to provide proper supports for the wires and cables that maypass therethrough. Subways or tunnels may be constructed witlrsuch alining, or any existing structure of this clraracter may be providedtherewith. The l ning may also be placed without instead of within, andserve as a means of Waterproofing.

Having thus described my invention, what I claim, and desire to secureby Letters Patent, 1s-

1. A subway, arch, tunnel, or similar structure provided with a layerof'terra-cotta lum bcr coated or saturated with asphalt, substantiallyas described.

2. A subway, tunnel, arch, orsimilarstruc ture, the innersurface ofwhich consists of or is lined with terracotta lumber coated or saturatedwith asphalt, substantially as described.

3. A subway, tunnel, arch, or'similar structure having an inner surfaceor lining formed of blocks of terra-cotta lumber coated or saturatedwith asphalt and bonded together with the same material, substantiallyas described.

vIn testimony whereof I have signed my name in the presence of twowitnesses.

CHARLES CARROLL GILMAN.

Witnesses:

THOMAS RIDER,

AMBROSE RIsnoN.

